1. Field of the Invention
In the field of oil and/or natural gas drilling, wellbores and wellbore conduits (see DEFINITIONS section) are known. The present invention relates generally to blowout preventers, and more particularly to a magnetically-controlled blowout preventer that employs a magnetic fluid in any of its construction and one or more magnets to control the flow of petroleum and/or natural gas effluent from an oil well.
2. Description of the Related Art
A Blowout Preventer (or BOP as it is sometimes called) is essentially a large valve used to seal off an oil or natural gas well. Sometimes, while drilling these wells, there are unexpected surges of underground pressure. These surges or “kicks” can force oil and/or natural gas into the wellbore uncontrollably. When this happens, it is customary to engage a Blowout Preventer which prevents the oil and/or natural gas from escaping into the environment.
Over the years, considerable progress has been made in the design, development, fabrication and deployment of Blowout Preventers. They are currently manufactured by several companies including: Cameron International (Houston, Tex.), Hydril Pressure Control (aka GE Oil & Gas of Houston, Tex.) and Shaffer (aka National Oilwell Varco of Houston, Tex.) among others.
There are two basic types of Blowout Preventers: the Annular type and the Ram type. In the Annular Blowout Preventer, one or more wedge-faced hydraulic pistons push against a doughnut-shaped elastomeric packing unit that squeezes against the drill pipe and BOP housing thereby sealing off the well. In the Ram Blowout Preventer, opposing steel plungers (also known as rams) are hydraulically forced together in the middle of the BOP housing thereby reducing flow. As a safety precaution, two or more blowout preventers are often combined into a stack to insure that the well can be sealed off in an emergency.
Blowout Preventers are quantitatively characterized by a number of different parameters such as their: pressure capacity, weight, design (annular versus ram), hydraulic requirements, electrical requirements, control system requirements (both electrical and acoustic), temperature requirements, riser interface, support frame(s), diagnostic systems, footprint, remote vehicle intervention compatibility and any number of other properties relating to how it is to be implemented (for example, lubrication, mud compatibility, salt-water compatibility, etc)
Over the years, engineers have strived to maintain mechanical simplicity in the design of Blowout Preventers in hopes of achieving ultra-high reliability as a fail-safe device. However, as natural resources become more scarce and drilling environments become more hostile and remote, control systems and necessary infrastructure become far more complex, thereby increasing the overall probability of an unforeseen event with potentially-catastrophic consequences. A particularly poignant example of this is the 2010 Macondo Well (aka Deepwater Horizon) Disaster in the Gulf of Mexico.
In U.S. Pat. No. 4,436,313 (“Tamama”), Tamama utilizes a Ferrofluid for sealing off a propeller shaft (on a ship) against the invasion of sea water. In his invention, 100 Å magnetite particles dispersed within a base liquid with surface-active agents was used in conjunction with longitudinally-spaced, annular, iron pole blocks and circularly-spaced permanent magnets fixed there between. Fundamental to Tamama's work is the necessity of the ferrofluid seal to remain in the liquid state in the presence of a magnetic field, so that the propeller shaft can rotate freely with little friction. However, in the case of a magnetorheological fluid, the seal would congeal into a solid plug in the presence of a magnetic field thereby prohibiting rotation of the propeller. And, while Tamama uses a form of magnetic fluid for sealing a propeller shaft of a sea vessel, he does not disclose the use of a magnetic fluid for sealing off a fluid conduit (such as an oil pipe).
In U.S. Pat. No. 7,021,406 (“406 Zitha”), 406 Zitha describes certain ways to use magnetorheological fluid for petroleum exploration. In his method, 406 Zitha employs an electromagnet at the bottom of the drill string (just above the drill head) to change the viscosity of magnetorheological drilling fluid for reducing the effects of water dilution and leak off from fractures in the stratum. However, nowhere does 406 Zitha disclose the use of a magnetic fluid for blowout prevention. 406 Zitha's bottom-up approach is fundamentally flawed for such purposes because it does nothing to protect against a blowout that might occur at any point above the electromagnet as a result of wellbore destabilization. In comparison, the Magnetorheological Blowout Preventer according to the present invention is a top-down approach (i.e. implemented at the top of the wellbore (in the casing or riser)) and thus serves to protect the entire length of the well against a blowout.
Other difficulties arise in 406 Zitha's approach when applied to preventing the flow of oil and/or natural gas along a wellbore. For example, in 406 Zitha, the electromagnet is located at the bottom of the wellbore, many thousands of feet into the earth where high-current electricity is nearly impossible to provide.
Another inconsistency in 406 Zitha's approach is that the electromagnet at the bottom of the drill string (just above the drill head) would have its strongest magnetic field in the hollow-center core through which the magnetorheological drilling fluid must pass. And thus, the same magnetic field to be used for mitigating the effects of dilution and leak off outside the drill string (that is, in the stratum where the strength of the magnetic field is weakest) would necessarily impose a tremendous burden of increased pressure for the mud pumps to overcome. All things considered, 406 Zitha's approach is not a viable option for reliably sealing off the full extent of an oil well in the event of a blowout.
The following published documents may also include helpful background information: (i) U.S. Pat. No. 2,609,836 (“Knox”); (ii) U.S. Pat. No. 7,300,033 (“033 Whitby”); (iii) U.S. Pat. No. 7,533,865 (“865 Whitby”); (iv) U.S. Pat. No. 7,032,670 (“670 Zitha”); and (v) pamphlet entitled “LORD MR Fluid demonstration Device” by LORD Corporation, dated 2006.
Description of the Related Art Section Disclaimer: To the extent that specific publications are discussed above in this Description of the Related Art Section, these discussions should not be taken as an admission that the discussed publications (for example, published patents) are prior art for patent law purposes. For example, some or all of the discussed publications may not be sufficiently early in time, may not reflect subject matter developed early enough in time and/or may not be sufficiently enabling so as to amount to prior art for patent law purposes. To the extent that specific publications are discussed above in this Description of the Related Art Section, they are all hereby incorporated by reference into this document in their respective entirety(ies).